Cleaning felts of paper machines



Sept. 18 1923.

G. K. WALKER CLEANING FELTS OF PAPER MACHINES 3 Sheets-Sheet 1 (juvemto'c 6607196 M/aZAer Filed Julv Sept. 18, 1923:

I G.,K. WALKER CLEANING FELTS OF PAPER MACHINES Filed July 26. 1921 3 Sheets-Sheet z irks a Sept. 18 1923. 1,468,057

G. K. WALKER CLEANING FELTS OF-PAPER MACHINES Filed July 26, 1921 3- Sheets-Sheet 5 cl i I I I o O o lo '0 o: 0 :0, :0: I w kavwemtoz Patented Sept. 18, 1923.

UNITED STATES PATENT OFFICE.

GEORGE K IMBALL WALKER, OF GLENS FALLS, NEW YORK. ASSIGNOB, BY DIRECT AND MESNE ASSIGNMENTS, TO GREAT NORTHERN PAPER COMPANY, OF MILLINOCKET,

MAINE, A CORPORATION OF MAINE.

CLEANING FELTS OF PAPER MACHINES.

Application filed July 26,

T 0 all whom it may concern.

Be'it known that I, Gnonon K, WALKER, a citizen of the United States of America, residing at Glens Falls, in the county of \Varren, State of New York, have invented certain new and useful Improvements in Cleaning Felts of Paper Machines; and I do hereby declare the following to be a full. clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the cleaning of felts of paper machines.

\Vhen the newly formed web of paper approaches the couch rolls from the forming part of the machine, its water content is about ninety per cent. The chief function of the machine from this point on is therefore to remove the water, and this is done by subjecting the web first to pressure and then to heat. The removal by heat is effected by passing the web over successive steamheated drying rolls. As the fuel cost for the generation of this steam is relatively high, it is obvious that the maximum possible quantity of water should be squeezed from the web before it is subjected to the more expensive drying operation. In removing the water by pressure, the web is supported upon successive porous felts which pass over suction boxes and between pressure rolls, and all of the water sucked and squeezed from the web during this treat ment must pass through these felts. In the interests of efficiency it is of vital importance that the felts be kept comparatively dry and porous and freed from the small particles of filler and fiber which are held within them as the water filters through. In fact, after the deposit ofthese small particles reaches a certain point the felts be come more or less impervious, the web crushes between the squeeze rolls,and operation must cease.

vVarious arrangements have been proposed 1921. Serial No. 487,672.

for cleaning the felts of paper machines, but the method commonly employed today for Fourdrinier machines is to stop the press parts of the machines, slacken the belts, release the pressure between the press rolls, rope up the felts and apply water to them to wash off the accumulation of dirt thereon. The usual method of cleaning the press or secondary felts of cylinder machines is to stop the regular operation for a period sufficient to remove and replace them with clean or new ones, the dirty felts being removed to detached washing vats for cleaning. These methods, although they may accomplish the end sought, introduce another inefficiency-loss of time. As the manufacturing operation must be discontinued during the felt-cleaning interval, and, as in the case of some kinds of paper it may be necessary to clean the felts one or more times day, it is clear that a considerable loss of production results when these methods are employed. a

Prior arrangements have been proposed for cleaning felts during the ordinary papermaking-operation ofthe machine but none of these arrangements is feasible for clean ing the felts of high speed modern Fourdrinier, Harper or cylinder machines. For example, it has been proposed to moisten the felt and then pass it inthe presence of water between kneading rolls or in contact with heaters to loosen and soften the deposited dirt, and the felt then run over a suction box and between squeeze rolls to remove the loosened dirt and the excess water., It has also been proposed to remove the dirt by directing jets of water or cleaning fluid with force against the felt and then removing the excess water by means of squeeze rolls and suction. Such .methods if used at all, were devised for use in connection with the slowly running machines of the past century, the felts of which ran at from 100 to 260 ft. per minute. With the advent of the modern high speed machine these methods have been discarded for the'more time consuming but safer methods discussed above, for when the felts in normal operation are running at from 600 to 1000 ft. per minute the use of beaters, kneading rolls or auxiliary squeeze rolls would lacerate and destroy the felt in a very short time, and without auxiliary squeeze rolls, it has formerly been considered impossible to remove the incidental cleaning liquid at each passa e of the rapidly moving felt past the cleaning device and thus retur itto the web in a substantially dry condition, a condition absolutely essen tial for successful operation. For these reasons no one prior to the present applicant has devised means for successfully cleaning the felts of modern high speed machines during their regular operation.

It is therefore an object of this invention to devise ways and means particularly adapted for cleaning the felts of modern high speed paper machines of all types during the ordinary paper-making operation of the machine without interrupting the continuity of the manufacturing operation or necessitating a reduction in speed. This object is attained by periodically applying a cleaning liquid to the dirty felts to soften the foreign ma terial deposited on them and at the same time applying a suction effectto the dirty side of the felts to withdraw both applied cleaning liquid and dirt without the assistance of other agencies. This suction is strong enough to remove substantially all of the applied liquid at each passage of the felt over it, although only a part of the dirt is removed at each passage. The suction is ordinarily applied by means of a suction box connected to a vacuum pump of suitable capacity and mounted for movement toward and away from the felt so that during the cleaning operation it may be moved into contact with the felt and removed from such contact when the cleaning has been effected.

The cover of the ordinary suction box used to withdraw water from the paper web is provided with a series of staggered holes. These holes soon fill up with lint, although contacting with the clean side of the felt and this lint must be periodically removed. W here the felts are being frequently roped up for washing this removal conveniently takes place during the felt washing operation. But a suction box designed for use as a felt cleaning agency comes in contact with the dirty side of the felt and would choke up in a short time if provided with a cover of staggered holes. Moreover, as the felts need not be removed for washing there is no opportunity for cleaning the cover. It is therefore important that the suction box used should be provided with a cover which shall not choke with lint and dirt from the felts. It it also vitally important that the box make a clean sweep of the felt, removing the dirt and applied water uniformly from the entire width and leaving no untouched streaks. A cover provided with staggered holes cannot do this. It is therefore a further object of this invention to design a suction box cover especially adapted foruse' in connection with felt cleaning. This object is in general attained by providing the cover with slots of proper size and arrangement as willbe described in detail later.

The particular nature of the invention, as well as other objects and advantages therewiil ppear more clearly from a descripof certain pref-erred embodiments of apparatus by which the method of the invention may be practiced. For the purpose of illustration the apparatus has been shown applied to a paper machine of the Fourdrinier type but it will be understood that it maybe applied to other types of machines by making necessary changes in the details of construction.

taken in connection with Fig. 2 shows'the couch rolls, press rolls'and felts of the machine, each felt having associated therewith the cleaning apparatus of the invention;

Fig. 3 is an enlarged view of the suction vex in transverse section taken on line 3-3 of Fig. l; Fig. i is a view of the box in longitudinal section; Fig. 5 is a plan view of the top of the box; Fig. 6 is a transverse section showing the relation of the felt to the top of the suction box during the cleaning operation; 7 is a plan View of a modified type of box top and Fig. 8 is a transverse section through a box provided with the type of cover shown in Fig. 7.

Since the parts of the paper machine shown in the drawings are of usual construction, they will not be described in detail, ex? cept in so'far as may be necessary for an understanding of the invention. first to Fig. 2, 10 represents a web of paper which after leaving the nourdrinier wire or screen and suction boxes passes between the couch rolls 11 onto the first felt 12 which is running in the direction of the arrows and carries the web over the usual suction box 8 and then between the first press rolls 13 and 14. "The felt travels over a number of rolls 15, one or more of which in accordance with the usual practice are adjustably mounted upon the frame 16 of the machine so that the tension of the felt may be adjusted.

After passing between the first press rolls the web is carried along by the felt and then transferred to the second felt 17 which carries the web over a second suction box 9 and between the second press rolls 18 and 19. The second felt 17travels over a num- Referring,

ber of rolls 20 one or more of which are adjustably mounted upon the frame of the machine.

After the web passes between the second press rolls it is lifted from thefelt 17 and carried over rolls 21 and 22, and then between the third press rolls 23 and M by means of a third felt 2-5 which passes over rolls 26 adjustably mounted on the framework of the machine. After passing between the third press rolls the web passes over a roll 27 and then to the drying cylinder 28, of which there may be any desired number according to the speed of the machine and characteristics of the paper which is being produced. Y

The apparatus thus far described is of standard construction and operates in the usual manner. In accordance with the present invention there is associated with each one of the felts a. suction or vacuum box 29 comprising a trough 30 having a slotted cover, the whole being movably mounted on the frame of the machine in position to be brought into engagement with the side of the felt to be cleaned when the felt occupies such a position that this side is turned downward. As shown herein the frame 16 on each side of the machine is provided with av pair of guides 31 between which the end of the suction box is mounted. The guides are connected at their lower ends by a brace 32 provided with a bearing 33 for a shaft 34 which extends from one side of the machine to the other and carries cams 35 which when the shaft is rocked by means of a Suitable handle 36 will raise the suction box into engagement with the felt or withdraw it therefrom, according to the position of the cams. It is, of course, understood that other means such as racks and found best adapted to the purpose.

The cover of the box in Figs. 3, 4, 5 and 6 comprises a series of parallel strips 42 spaced apart by blocks 43 and spa ing sleeves 44, mounted upon suitable reinforcing bolts, to form a series of slots extending transversely of the felt the entire width thereof. As stated above, the use of a series of staggered small holes has proved unsatisfactory for the reason that these holes, unless too large to be feasible, soon clog with lint and dirt and thus become ineffective. The same would be true of slots if too narrow, and a. satisfactory arrangement has been found to be that of two slots, each about two and one-half inches wide and spaced part about two inches, as shown in Fig. 5.

Although a box cover of the type shown in Fig. 5 may be effectively employed, it is often desirable, especially when working with closely woven felts, to employ a attached thereto by screws or in any other convenient manner. \Vhen in place the flat.

face of each of the units forms in connection with the recess of the adjacent unit a narrow aperture which will lie at an angle to the direction of the felt asit passes over the snot-ion box in the direction indicated by the arrow on Fig. 7. The strips constituting one-half of the cover are inclined in the opposite direction to those constituting the other one-half. This leaves a triangular space at the center of the cover which is filled by a triangular piece 53, provided with a. number of slots 54 lying parallel to the slots of the units. The diverging slots of this cover are arranged so that the effective length of one overlaps the effective length of those immediately adj acent with the result that the entire width of the felt is subjected to suction as it passes over the box. This is very important, as even one dirty or wet streak in a felt will ruin the paper. Although the dimensions This cover consists of anumber of of thiscover may be varied, satisfactory rean angle of from. 15 to 20 to the line of travel of the felt. 7

It sometimes happens where a relatively high vacuum is employed that the spreading action of the diverging slots causes the portions of the felt contacting with them to follow along the slots, so that the parts of the felt initially cont-acting with the solid strips of blocks 50 pass from the box without having been subjected to the sucking action of the box, or at least without having been subjected to it for a sufficient lengthof time for effective cleaning. felt thus returns to pick up the web in a streaked condition. To prevent this the box has been provided with an auxiliary slot The 55 extending across the full width of the Two inches has proved to be a suitable width for this auxiliary slot.

Where thesuction box is mounted in such a manner that some runs of the felt are beneath it, as is the case in the arrangement shown in Fig. 1, the dirt and water rubbed off by the outer edges of the box drip downwardly upon the felt. In order to avoid this suction boxes so mounted are provide with inclined troughs 4:8 aflixed to their sides, which troughs catch this drip and lead it away. Where the boxes are mounted near the bottom of the machine and entirely below the felts, as shown in Fig. 2, these troughs are unnecessary.

For the purpose of supplying water or cleaning solution to the felts, a pipe 45 provided with a number of apertures or 1102-.

Zles is arranged between two of the runs of the felt and may apply the water either directly to the felt itself or indirectly by spraying it upon one of the rolls over which the felt passes. Both arrangements have been shown in Figs. 1 and 2. This water may be applied to either or both sides of the elt, and this also has been illustrated. The pipe 45 should preferably be provided with a connection lG leading to the usual water supply of the mill, and a connection t? for supplying warm or hot water with or without a mixture of chemicals in proper dilution for aiding or accelerating the washing without detriment to the stock of paper being made. This water should be applied at a point sufficiently in advance of the suction box to permit the water to become uniformly distributed over the face of t e felt in order that it may have an opportunity to loosen the dirt thereon, but not so far in advance of the box as to enable the water to drain from the felt before reaching it. The particular point at which the water should be supplied will depend upon several factors, such as the speed of the machine, porosity of the felt and the amount of residue deposited upon the felts as determined by the character of paper being produced on the machine.

lVith felts running at about 650 ft. per minute, the best practice requires the application of from three and one-half to four gallons of water or cleaning liquid per minute on a 120 inch machine... In order to remove substantially all of this water a strong suction is required. To meet this requirement the vacuum pump should draw through the felt about two and one-half cubic feet of air per minute per lineal inch in width of exposed felt. Thus for a 120 inch machine, the pump should be discharginn: in round numbers about three hundred cubic feet of air per minute.

There is, of course. no absolute standard of cleanliness, but the apparatus, if funcwithin reasonable limits.

tioning properly, should remove enough of the dirt in from twenty to thirty minutes to enable the felt to operate with reasonable efficiency as a medium for the passage of water from the web. The quantities of water and air given above have been found satisfactory but, of course, may be varied In determining upon a practical minumum it must be borne in mind that the air must not only remove substantially all of the dirt during the whole cleaning period, but that it must remove substantially all of the applied cleaning liquid at each passage of the felt over the box. If it does not do this the web will crush and the paper will be ruined.

During the cleaning period when the felt is passing over the top of the box and the vacuum pump is in operation, the air being drawn through the felt presses it into the slots of the box cover as shown, for example, in 6. By virtue of these de pressions, the upper edges of the strips 42 or of the blocks 50 exert a rubbing or scrub bing action upon the felt and undoubtedly remove some of'the loosened and softened dirt in this manner.

In the operation of the apparatus described above, the web of paper travels through the machine in the usual manner. and whenever foreign matter accumulates upon the felts of the machine to a sufficient xtent to prevent the water from properly draining from the web, the felts may be cleaned without interfering with the continuouspapenmaking operation of the chine. Water or a suitable cleansing solution is admitted to the pipe 45 associated with the felt to be cleaned and is distributed over the surface of the felt, thus tending to loosen the material deposited thereon. At the same time the corresponding suction box 29 is lifted into engagement with the felt and placed in communication with the main 41 so that a suction effect is produced tend- .ing to depress the felt into the slots of the box cover and by drawing air through it remove from it all of the applied water and a part of the foreign material. l i here the felt is traveling at 650 feet per minute and the cleaning period lasts for say 20 minutes, a given point on the felt travels 13,000 feet. The approximate average length of such felts is fifty feet. This means that a given point on the felt passes the suction box 260 times during the cleaning interval. At each passage over tie box a small quantity of the dirt is removed and so eventually the felt runs practically clean.

Atevery passage ver the box. however, substantially all of the applied water is removed.

Although the use of suction or partial vacuum has been instanced and considered most feasible, it is yet obvious that the same result mightbe obtained by the use of posipump, and sucha modification is considered to be embraced within the broadest aspect' of this invention. The invention hasbeen shown and described in connection with a paper machine of the F ourdrinier type, but it is'to be understood that itis equally applicable to paper making machines of every type, it being necessary only that the supply pipes and suction boxes be arranged in proper relation to the felts to be cleaned. It will also be understood that various changes of construction of the apparatus may be made without departing from the principles of the invention as defined in the appended claims. q

This application is a continuation in part of Serial No. 381,314, filed May 14, 1920.

I claim:

1. The method of cleaning the felt of a paper machine in which the felt is. moving at relatively high speed which consists in' supplying a cleansing liquid to the felt to loosen foreign material thereon, and removing the liquid and foreign material therefrom by the sole application of a suction effect.

2. The method of cleaning the felt of a paper machine which consists in supplying a cleansing liquid to the felt to loosen foreign material thereon, and applying a suction effeet to the felt along lines of action which diverge with respect to the direction of travel of the felt in order to open the meshes of the felt and remove the liquid and foreign material therefrom.

3. The method of cleaning the felt of a paper machine which consists in supplying cleansing liquid to one of the rolls over which the felt travels to cause the liquid to be distributed over the felt and loosen foreign material thereon, and applying a suction effect to the side of the felt upon which the liquid is distributed to remove the liquid and foreign material therefrom.

4:. Apparatus for cleaning a felt of a paper machine comprising in combination, means for supplying cleaning liquid to the felt to loosen foreign material thereon, and a suction box having a cover adapted to engage the felt and provided with a. plurality of diverging slots, and means for creating a vacuum in the box whereby the suction effect acting through the slots will spread the felt and remove liquid and foreign material from the meshes thereof.

5. A suction box for use in cleaning felts of paper machines comprising a trough hav ing a cover provided with a plurality of strips, each having a recess extending part way along one side thereof, the strips constituting one-half of the cover being inclined in the opposite direction to those constituting the other half and the straight, side of each strip forming in conjunction withthe recessed side of an adjacent strip a slot through which the suction effect may be exerted upon the felt as it passes over the cover, and a member filling the triangular space between the halves of the cover and provided with slots lying substantially parallel to the slots formed by the strips.

6. The method of cleaning paper machine felts during the ordinary paper-making operation of the machine and while said felts are traveling at speeds of live hundred feet per minute or more which consists in applying a cleaning liquid to the felts to soften the deposited dirt and then removing the softened dirt and cleaning liquid by the sole application of a suction effect.

7. The method of cleaning the felt of a paper machine which consists in supplying cleansing liquid to one of the rolls over which the felt travels to cause the liquid to be distributed over the felt and loosen foreign material thereon, and applying a suction effect to the felt to remove the liquid and foreign material therefrom.

8. The method of removing dirt from the felt of a paper machine in which the felt is moving at relatively high speed during the ordinary operation of the machine, which comprises applying to the felt a cleaning liquid to soften the dirt, and a suction effect strong enough to remove substantially all of the applied liquid and a part of the deposited dirt at each passage of the felt over it.

9. A suction box for use in connection with paper machine felts having a cover adapted to engage the felt and provided with a plurality of diverging slots and a longitudinal slot extending transversely of the felt, the felt passing first over the diverging slots and then. over the longitudinal slot.

10. A suction box for use in connection with paper machine felts having a cover adapted to engage the felt and provided with a plurality of diverging slots and a longi gudinal slot extending transversely of the elt.

11. A suction box for use in connection with paper machine felts having a cover adapted to engage the felt and provided with a plurality of diverging slots and a longitudinal slot extending transversely of the felt the entire width thereof.

' 12. In an apparatus for cleaning a felt of a paper machine comprising in'combination means for supplying cleaning liquid to the felt to loosen foreign material thereon and a suction box having a cover adapted to engage the felt and provided with a plurality of diverging slots and a longitudinal slot liquid and foreign material from the meshes thereof, and acting through the longitudinal slot will remove all streaks which may have passed the diverging slots.

13. In an apparatus for cleaning the felts of paper machines While in continuous operation, a suction box having an inclined open trough aflixed to its side to catch and lead away the drip from the Wet feltpassing over it.

14. A suction box for use in connection with paper machine felts having an inclined trough aflixecl to its side to catch the drip from the Wet felt passing over it.

In testimony whereof I afiix my signature;

GEORGE KIMBALL WVALKER. 

